Subepidermal cannular instrument and method for automated determination of bleeding time and blood loss

ABSTRACT

A cannular medical instrument and an automated method is disclosed herein for accurately determining bleeding time and blood loss. The main body of the instrument is in many respects similar to an elongate hypodermic needle having a predetermined opening made in the side thereof near the tip defining cutting edges and leaving a &#39;&#39;&#39;&#39;pickup&#39;&#39;&#39;&#39; length of usually approximating less than 10 mm. Alternatively to the formation of the opening, the bevel of a standard hypodermic needle may be extended until the desired opening is present. The forward portion and tip of the tubular needle in use is inserted beneath the skin at an optimum location which may be subcutaneous or in another position subepidermal. The central and rear portion of the elongate tubular needle is disposed in use externally of the skin and has connection means for receiving a small conduit connected with a predetermined suction source for withdrawal of liquid. Closely combined with said hollow needle is a tubular branch connection element for supply of distilled water or other fluid at the area of the incision made and &#39;&#39;&#39;&#39;pickup&#39;&#39;&#39;&#39; area. Preferably this branch tubular connection is rigidly integrated with the main body or tubular needle and extends angularly thereto with a terminal connection for receiving a small supply conduit from a controlled source of distilled water or other liquid or fluid at a predetermined speed and volume. To this structure and the subepidermal insertion of the cannula, a pickup is made of mixed blood and distilled fluid at the predetermined incision area and the amount of blood loss is then measured electrically or electronically and the duration of reading is also recorded.

Waited States Patent [191 Friedell [4 1 Oct. 15,1974

[ SUBEPIDERMAL CANNULAR INSTRUMENT AND METHOD FOR AUTOMATED DETERMINATION OF BLEEDING TIME AND BLOOD LOSS [76] Inventor: Peter E. Friedell, 362 Elton Hills Dr., Rochester, Minn. 55901 22 Filed: Nov. 15, 1972 21 App1.No.:306,628

[52] U.S. Cl 128/2 G, 128/221, 128/240 [51] Int. Cl A6111 5/00 [58] Field of Search 128/2 R, 2 G, 221, 276,

[56] References Cited UNITED STATES PATENTS 2,137,132 11/1938 Cooley 128/221 Sutor et al. Amer. Jour. Clinical Path. Vol. 55, May 1971 pp. 541-550.

Primary Examiner-Dalton L. Truluck Attorney, Agent, or Firm-Williamson, Bains & Moore [5 7] ABSTRACT A cannular medical instrument and an automated method is disclosed herein for accurately determining bleeding time and blood loss. The main body of the instrument is in many respects similar to an elongate hypodermic needle having a predetermined opening made in the side thereof near the tip defining cutting edges-and leaving a pickup length of usually-- approximating less than 10 mm. Alternatively to the formation of the opening, the bevel of a standard hypodermic needle may be extended until the desired opening is present. The forward portion and tip of the tubular needle in use is inserted beneath the skin at an optimum location which may be subcutaneous or in another position subepidermal. The central and rear portion of the elongate tubular needle is disposed in use externally of the skin and has connection means for receiving a small conduit connected with a predetermined suction source for withdrawal of liquid. Closely combined with said hollow needle is a tubular branch connection element for supply of distilled water or other fluid at the area of the incision made and pickup area. Preferably this branch tubular connection is rigidly integrated with the main body or tubular needle and extends angularly thereto with a terminal connection for receiving a small supply conduit from a controlled source of distilled water or other liquid or fluid at a predetermined speed and volume. To this structure and the subepidermal insertion of the cannula, a pickup is made of mixed blood and distilled fluid at the predetermined incision area and the amount of blood loss is then measured electrically or electronically and the duration of reading is also recorded.

7 Claims, 8 Drawing Figures SUBIEPIDERMAL CANNULAR INSTRUMENT AND METHOD FOR AUTOMATED DETENATION OF BLEEDING TIME AND BLOOD LOSS BACKGROUND OF INVENTION In pathology and surgery skin bleeding time is one of the oldest tests for blood clotting. It is intended to measure the complex interaction between intrinsic and extrinsic clotting factors. The extrinsic clotting factors comprise blood platelets, capillary integrity and supporting connective tissues. In all of the prior art known to me, including two rather recently developed improvements in method and automation, an incision of preferably a predetermined length and area was made in the skin itself and the exuded blood was picked up and measured from this incision area.

Two possible parameters can be measured during the bleeding time. They are first the length of time during which bleeding occurs and, secondly, the amount of blood loss sustained during that time. In the prior art, including recent improvements of technique, the duration of bleeding time has been the additional parameter measured. The amount of blood loss has been far too small to measure accurately and of course duration of bleeding may be within the normal range while amount of blood loss may far exceed the normal range.

The most difficult problem in the past has been the standardization of a skin incision. Several devices have been made with the intention of creating a standard skin incision but because of wide variability of human skin they have met with little success.

Rather recently a blood testing method and the physical means employed were described in a report and article appearing in Volume 55, starting page 541 of the American Journal of Clinical Pathology, 1971. The article was prepared by several able doctors in the Mayo Graduate School of Medicine at the University of Minnesota and also Department of Clinical Pathology of the Mayo Foundation, Rochester, Minn. An incision through the skin by lancet was made to a stab depth of 5mm. Thereafter a transparent flow cube was taped over the incision and the blood flow mixed with distilled water was metered and recorded. Another published article showing a template system for the old time standardized Ivy bleeding time system was published in August, 1969, in the publication Blood, Volume 34, No. 2, entitled The Standardized Normal Ivy Bleeding Time and its Prolongation by Aspirin. Several doctors from a number of medical schools and centers jointly contributed this article.

Very recently (published in September, 1972) in Volume 58, No. 3, an article appeared in American Journal of Clinical Pathology entitled Electronic Method for Quantitation of Bleeding Time. This article, published by eminent doctors of Mayo Clinic and Mayo Foundation of Minnesota, described bleeding tests made through the skin similar to the previously reported article in Volume 55, starting page 541, of the American Journal of Clinical Pathology. However, this recent article employs and describes one of the electronic systems for determining conductivity of a flowing blood mixture and for charting or recording fluctuations and intensities of blood mixtures which I have favorably used as one alternative with my novel instrument and system.

While the calibration, conductivity measurements and chartings as disclosed in said recent article, Volume 58 (American Journal of Clinical Pathology), are quite accurate for quantitatively measuring volume of blood loss, the system which employs a stab, predetermined incision through the skin and a pickup above the skin employing a Lucite cube taped to the skin, fail, in my tests and experience, to give accurate evaluations for determining hemostatic abnormalities. Such failure, or at least partial failure, is partly because of the very great variation in skin structure on morphology in different human beings. Furthermore, the incision made by stab action cuts relatively few capillaries, while with my instrument applied substantially parallel below the skin many more capillaries are cut.

The problem, which I faced, consisted in discovering a system and method of making a precise predetermined incision in a capillary bed where variability of human skin would have no influence or factor in accurate measurement of the blood loss or clotting or bleeding time and where a predetermined pickup area was formed to permit readily automated determination of not only bleeding time but blood loss by pickup and withdrawal of a mixture of blood and thinning and conveying medium, such as distilled water or other controlled flow of liquid.

I believe I have successfully solved the problems of the prior art by discovery and conception of a cannular instrument and its application subepidermally to define, below skin level, an incision and pickup area with provision of measured conveying liquid, such as distilled water, directly to said area and with withdrawal of the mixture of blood and carrier or conveying liquid from the pickup area. My system and method, after accurate and measured withdrawal, from said pickup area may utilize electronic measuring and timing devices for accurately determining the quantity of blood emitted before the incision clots, as well as the actual time of bleeding from the instant the incision is made.

SUMMARY OF INVENTION Several embodiments of the invention are disclosed in the following pages hereof. They all have in common certain essential cooperating components and require, in use, a source of supply of a predetermined small flow of thinning (or mixing) liquid, such as distilled water, and a source of suction or negative pressure maintained at a predetermined level for withdrawal of a mixture of emitted blood and mixing liquid, together with electrical or electronic means for measuring or indicating the conductivity of the mixture withdrawn, or, in the alternative, a color intensity measuring means.

In all forms of my invention, an elongate cannular, multi-functional instrument is essential, having a forward piercing point extremity with predetermined incision means cooperating therewith which actually predetermines the length and width of an incision made in a capillary flesh bed disposed below or inwardly of the human skin. The pointed extremity of the body and the immediately adjacent incision area of the instrument must be capable of readily penetrating the skin and thereafter being turned and subepidermally (such as subcutaneously) inserted for operation. The incisionproducing means of the elongate body defines a vacuum, pickup area or shallow chamber which is in communication with the hollow interiorof the body to provide for withdrawal of a blood and liquid mixture axially of the remainder and rearward part of the body.

The rearward and, in fact, central portion of the body when the instrument is used is disposed outwardly of the skin of the human arm or other body member from which blood is to be withdrawn, and near the rear portion thereof or extremity of the body, a sealed connection is provided for connection with a predetermined source of suction or negative pressure.

The instrumentation of my invention further requires a supply-conduit means preferably having rigid connection with the body memberand provided with a discharge mouth or orifice disposed in operation below the human skin and in communication with the pickup and mixing area previously described. The source of liquid supplied to said supply conduit means must be predeterminately conditioned and metered for a predetermined very small quantity flow rate while the test is being taken.

Visual means, such as a flow cube, may be employed, if desired, attached with the withdrawal conduit of the system, and a delicate sensing medium may be provided, by stylus or otherwise, for indicating up and down fluctuations in the conductivity or color of the mixture withdrawn.

With the foregoing essential components of the instrument and proper controls for the source of mixing and carrier liquid (such as distilled water) supplied, and meters for detecting the relative proportion of emitted blood in the mixture during flow or even after collection, I have found by actual tests that not only the bleeding time but also the blood loss or emission may be accurately determined.

With further reference to the multi-functional cannular body of my instrument, it is essential for accuracy that the incision be made subepidermally and that it be of a predetermined length and width. It is further essential that in the tests the piercing of the skin or any incision made on the skin be entirely ruled out as to affect on the functional operation of my device and method.

It is to be understood that with the employment of proper testing apparatus, such as a spectrophotometer, and a proportioning pump of an Auto Analyzer, continuous readings may be obtained during the bleeding period, which will show the individuals bleeding pattern as well as bleeding intensities.

DETAILED SPECIFICATION Several embodiments of my invention, including cannular instrument and system, will hereafter be described in connection and relation to the patent drawings wherein like reference characters refer to similar parts throughout the several views and in which:

FIG. 1 is a side elevation on a substantially enlarged scale of one embodiment of my cannular instrument;

FIG. 2 is a cross section on a still larger scale taken along the line 2-2 of FIG. 1, looking in the direction of the arrows;

FIG. 3 is a bottom elevation of the instrument shown in FIGS. 1 and 2;

FIG. 4 is a side elevation of a second embodiment of my instrument;

FIG. 5 is a side elevation, on an enlarged scale, of a third embodiment of the cannular instrument;

FIG. 6 is a side elevation, on an enlarged scale, of a fourth embodiment of my cannular instrument wherein metal conductive parts of the elongate body are rigidly interconnected by a medially disposed sleeve constructed of high-grade electrical insulating material. The metal parts span a liquid mixture flow and act as sensors in an electrical circuit through a sensitive meter, thereby producing accurate measuring of blood proportions contained in the flowing hemolyzed mixture;

FIG. 7 is a schematic diagram of a system forcontrolled supply and conditioning of a flow-vehicle mixing liquid (such as distilled water) together with controlled negative pressure for withdrawal of a hemolyzed mixture; and metering and production of chart recording of percentage of blood exuded and intensities of blood exusion; and

FIG. ,8 illustrates a chart recording of a test.

Referring now to the embodiment of my cannular instrument and its connections shown in FIGS. 1 to 3 inclusive, an elongate multi-functional hollow body 10 is provided resembling, in many respects, a hypodermic needle of approximately 19 gauge. The forward end of the body 10 is sharply pointed for penetration through and then in close relation parallel to the skin or at least in a subepidermal pattern. The forward end of body 10 in this embodiment is provided with a solid or dam portion 10a defining with a rearwardly cutout portion a forward shoulder 10b for defining the forward end of a predetermined incision, and also the forward endof a pickup chamber 11 which is made through the underside of the tubular'body by a predetermined slit (in a range somewhat below 10 mm) leaving horizontal edge portions of the thin tubular body to actually define the incision in a capillary bed of tissue made somewhat below the skin surface through which the needle portion is projected. The relative sharp edges which define the incision area and also the pickup area 11 are predeterminately spaced apart preferably at one mm to determine the width of the incision. The central portion of the body serves as a withdrawal port when negative pressure is applied, and at the rear end of body 10 is disposed an enlarged and thickened fitting 12 by which a connection may be made in the outer portion 12a thereof with a small flexible withdrawal conduit 13.

For supplying a predetermined and controlled flow of mixing and carrier liquid centrally of the pickup chamber 11, a second cannular liquid supply element or hollow needle 14 is employed, the usually sharpened outer portion 14a thereof being inserted bodily through the medial portion of the tube of body 10 and positioned and fixed against or at least very close to the unslotted upper portion thereof. Portion has a discharge mouth 14b disposed substantially centrally of the pickup area 11. The media] portion of needle member 14 is bent angularly, as clearly shown in FIG. 1, and has a surrounding relatively thick connection fitting l5 surrounding its outer extremity and carrying near its outer terminal a connection fitting which may be readily cou pled in sealed relation with a small flexible supply tube 16.

It will be understood that the cannular instrument of the first embodiment described is to be employed and controlled by recording systems later to be in detail described in this specification.

It is pointed out that the instrument of the first embodiment performs several important functions. First the needle or point of the tubular body enables the forward part of body to be readily, with little pain, passed through the several layers of the human skin and thereafter turned subcutaneously or at other positions subepidermally. Secondly, inward thrust subepidermally causes the edges 100 to define the width of the incision. The shoulder 10b with the rearward shoulder 011 of the pickup area defines the length of the incision and similarly defines a positively predetermined pickup chamber 11 disposed in juxtaposition and above the capillary tissue bed. The medial portion of body 10 is positioned under the skin with the open area 11 facing away from the skin surface. Thirdly, the body 10 serves as the handle of the instrument together with the rigidly connected fitting 15 of the liquid supply tube to obtain accurate injection and subepidermal placement of the needle portion. The hollow body 10, with its connection fitting 12, serves as a withdrawal passage for connection with a flexible back pressure or negative pressure withdrawal tube. The needle-like supply portion 14, with the discharge mouth 14a, functions to direct entrance of a mixing and carrier liquid at the very area of the vacuum pickup.

Referring now to the form of the invention illustrated in FIG. 4, the body 20, the supply needle-like element 14 and the connection elements are substantially identical with those described in relation to FIGS. 1 to 3, inclusive. However, instead of employing at the piercing portion or point of the needle a closure or dam 12a, the hollow needle at its forward end is beveled or cut at its underside at a small acute angle with some curvature to cause a point just inwardly of the piercing point a to form the forward shoulder of the pickup chamber communicating with the interior medial portion of the hollow body 249. The end of the cut portion, identitied as 2%, defines the rear shoulder and the distance of the shoulder 20b from the underside of tip portion 20a should be precisely predetermined preferably within a range of from 5 to 10 mm. The beveling of the needle portion leaves incision-defining edges 20c disposed just above or in the capillary bed where the incision is made. The spacing apart of the two elongate edges Ztic determines the width of the incision which should be preferably precisely 1 mm.

Referring now to the embodiment illustrated in FIG. 5, the cannular body is provided, being in most respects identical with the body 10 of the first form of the invention described. Said body 30 has at the sharply pointed tip portion a damming element 30a, and a laterally communicating elongate slot in the bottom part of body 3% which defines the pickup area 32. In this form the supply needle 31 is bent at an angle, which is disposed and secured externally of the forward portion of the body 39 and then in tubular form is bent downwardly and enlarged or spread to form a discharge port 31b communicating with the central and upper portion of the pickup area 32 which of course also acts as the mixing chamber.

Referring now to the cannular instrument illustrated in FIG. 6, provision in this structure is made for providing sensors for an electrical flow meter with electrical connections extending from the forward or tip portion (conductive metal) 400 through electrical wire W, the forward tip portion 40a being rigidly interconnected with the medial and rearward portion 40b of this embodiment by a substantially rigid tube connection element 41 which is constructed of a suitable hard plastic or other material having high insulating qualities for electricity. The other features of supply of control liquid carrier flow, and withdrawal of mixture tube and means, are substantially similar to the corresponding means shown in the other embodiments described.

Referring now to FIG. 7 of the drawings which diagrammatically indicates one general system which is found highly satisfactory for use with the employment of my novel instrument, the instrument is diagrammed in the central portion of the view having the body 10, as shown, and providing the mixing chamber and pickup space 11. The liquid supply tube 14 is connected with a controlled liquid supply, usually distilled water, indicated in the block entitled Water Supply on the drawings. It will be understood that with the supply of proper distilled water it is preferable, by induction of air into the stream which passes through conduit 50, to introduce air which will form, in the moving stream of water, bubbles.

The diagram mixing chamber of course includes at the lower defining portion thereof the actual incision made by the instrument and the exuded blood and water introduced through tube 14 admix and are drawn off in the direction of arrow 51 by an air pump, so indicated on the drawings. The air pump is carefully calculated for withdrawal of a predetermined stream of the mixture and the discharge of the pump passes, as shown in arrows 52 and 53, to a mixing coil which may, if desired, contain temperature control and usually constitutes a tortuously arranged tubular mixing means or may constitute the transparent flow block such as is described in the article identified under the term Background of Invention which was recently published in the American Journal of Clinical Pathology, Volume 58, No. 3, issued in September, 1972.

The flow from the mixing coil then passes into a suitable bubble remover, which may consist simply by splitting the stream of flowing blood wherein the air and bubbles of course go to the top by gravity. The top stratum is thereby exhausted, being sure that all heavier liquid passes from the bubble remover into the electronic conductimeter, so designated in FIG. 7. This electric conductimeter includes sensing elements with suitable amplification to variably indicate conductivity of the passing bloodstream as it is sent by two spaced conductive electrical sensors. The actual apparatus employed in this conductimeter may be substantially identical with the apparatus disclosed in pages 256 through 258 of said very recent article published in Volume 58, No. 3, September, 1972, of the American Journal of Clinical Pathology. The indications and results of mea suring conductivity of the mixed flowing stream of distilled water and blood are transmitted to a conventional type of chart recorder, such as illustrated in said last mentioned article wherein progressively, during flow, a stylus or pen inscribes upon a graph sheet the varying intensities of the blood in the mixture during the duration of the period. The waste from the flow through the conductimeter as shown is pumped out and either dissipated or retained for further measurements and conductivity if desired.

It will be understood that while I have found the foregoing instruments and system highly successful for the use of my instrument and the method involved in using my instrument, other instruments may be used for determining by percentage or otherwise the amount of blood contained in proportion to the water of the mixture. For example, a spectrophotometer and a proportioning pump of an autoanalyzer may be substituted for the conductimeter employed as may be other instruments for determining intensity of color and recording of variation of intensities of color during the flow of the withdrawn mixture of blood and distilled water or other conveyor liquid employed.

In making a test, the forearm of a patient is a favorable part for the incision. A blood pressure cuff is employed maintained at an inflative pressure of about 40 mm Hg. A site between the wrist and elbow is selected and, after cleansing, my instrument is carefully inserted subcutaneously and otherwise subepidermally, but in a direction below the skin to cut a great multiplicity of the minute capillaries which extend perpendicularly to the skin. Such transverse cutting of many capillaries has a great advantage for blood test accuracy compared with a skin incision made stabwise as is employed in the prior art.

The supply of distilled water with bubbles therein, the mixing of exuded blood and liquid, withdrawal of the mixture and removal of bubbles thereafter proceeds as previously described. The mixture, after removal of bubbles, passes through the conductimeter and thereafter recordings and fluctuations are made in graph form by the chart recorder. FIG. 8 illustrates a typical rather normal test showing bleeding time, intensities and pattern. Normal values may be compared with those having unusual characteristics. The accurate and full tests appear highly useful in evaluating hemostatic abnormalities and diagnoses.

What is claimed is:

1. In a withdrawal system for determining bleeding time and blood loss, a pickup and withdrawal instrument comprising:

an elongate cannular body having a pointed forward extremity for piercing skin and tissue,

said body having an elongate side opening defined by a pair of parallel, longitudinal cutting edges and a rear shoulder to define a pickup and mixing area of predetermined dimension, and in communication with the interior of said body,

manipulating handle means extending angularly from said body and disposed rearwardly of said pickup area to enable said cannular body to be turned and longitudinally projected substantially parallel to the skin surface after first penetration through the skin,

said body having means at its rear portion for connection with a suction conduit to effect withdrawal of a mixture of emitted blood and a mixing and carrier liquid, and

controlled liquid supply means having a discharge disposed in said pickup area for causing mixture of supplied liquid with blood in said area.

2. The structure and combination set forth in claim 1 wherein said liquid supply means includes a tube connectible with a flexible conduit for predetermined sup-. ply of liquid for mixing and carrying expelled blood, said tube having rigid connection with said body and having a discharge opening interiorly of said body and communicating with said pickup area.

3. The structure and combination set forth in claim 1 wherein said side opening of said body is elongate starting at a point close to the forward extremity point and extending rearwardly to an area-defining shoulder through a length within a range less than 10 mm, said opening defining an elongate slot having a width approximating 1 mm, and

the discharge of said liquid supply means being opposed to said slot which defines said opening and pickup area.

4. The structure and combination set forth in claim 2 wherein said rigidly secured supply means-tube and the rear of said cannular body constitute a handle for manipulating said instrument to readily provide for insertion thereof subepidermally, and

wherein the forward portion of said cannular body forwardly disposed of the juncture of said body with said tube is in operation inserted subepidermally for blood testing.

5. A pickup and withdrawal instrument for use in a system which provides for automated determination of bleeding time and blood loss,

said instrument comprising an elongate cannular body having a pointed forward extremity for piercing skin and tissue,

said body having a side opening disposed somewhat rearwardly of said piercing extremity for defining a mixing and pickup area of predetermined length and width,

said body having means at its rear portion for connection with a suction conduit to effect withdrawal of a mixture of emitted blood and a mixing and carrier liquid,

controlled liquid supply means having a discharge disposed in said pickup area for causing mixture of supplied liquid with blood in said area, said instrument comprising part of a system which employs an electronic instrument for measuring electrical conductivity of the flowing mixture of blood and liquid withdrawn from said body, and

wherein, as electrical sensors for said instrument, the

tip portion of said body is constructed of an electrically conductive metal and the rear portion of said body is also constructed of an electrically conductive metal, and

the interconnecting medial portion of said body is constructed of a substantially rigid material having substantially no electric conductive qualities, and

electric conductors extending from said forward and rearward portions of said body to terminals of said instrument.

6. A new method for automated determination of bleeding time and blood loss which consists in:

forming a penetration in capillary tissue subepidermally with a cannula to form an incision in said tissue of predetermined length and width, said cannula being provided with a piercing tip and a side opening spaced therefrom, said side opening having longitudinal cutting edges and at least one shoulder defining the boundaries thereof, said can: nula being inserted into said tissue in a direction substantially parallel to the skin with the side opening facing away from the skin so that the incision is formed along the bottom surface of the penetration, said cannula further providing a mixing and pickup space in said penetration directly above said incision formed by the boundaries of said side opening,

supplying a predetermined small flow of a mixing and carrier liquid to said pickup space, withdrawing 7. The combination of steps set forth in preceding claim 6 wherein said instrumentation includes in the withdrawn flow of emitted blood and carrier liquid, the passing therethrough of an electrical current with suitable sensors to determine change in the conductivity of the mixture during flow. 

1. In a withdrawal system for determining bleeding time and blood loss, a pickup and withdrawal instrument comprising: an elongate cannular body having a pointed forward extremity for piercing skin and tissue, said body having an elongate side opening defined by a pair of parallel, longitudinal cutting edges and a rear shoulder to define a pickup and mixing area of predetermined dimension, and in communication with the interior of said body, manipulating handle means extending angularly from said body and disposed rearwardly of said pickup area to enable said cannular body to be turned and longitudinally projected substantially parallel to the skin surface after first penetration through the skin, said body having means at its rear portion for connection with a suction conduit to effect withdrawal of a mixture of emitted blood and a mixing and carrier liquid, and controlled liquid supply means having a discharge disposed in said pickup area for causing mixture of supplied liquid with blood in said area.
 2. The structure and combination set forth in claim 1 wherein said liquid supply means includes a tube connectible with a flexible conduit for predetermined supply of liquid for mixing and carrying expelled blood, said tube having rigid connection with said body and having a discharge opening interiorly of said body and communicating with said pickup area.
 3. The structure and combination set forth in claim 1 wherein said side opening of said body is elongate starting at a point close to the forward extremity point and extending rearwardly to an area-defining shoulder through a length within a range less than 10 mm, said opening defining an elongate slot having a width approximating 1 mm, and the discharge of said liquid supply means being opposed to said slot which defines said opening and pickup area.
 4. The structure and combination set forth in claim 2 wherein said rigidly secured supply means-tube and the rear of said cannular body constitute a handle for manipulating said instrument to readily provide for insertion thereof subepidermally, and wherein the forward portion of said cannular body forwardly disposed of the juncture of said body with said tube is in operation inserted subepidermally for blood testing.
 5. A pickup and withdrawal instrument for use in a system which provides for automated determination of bleeding time and blood loss, said instrument comprising an elongate cannular body having a pointed forward extremity for piercing skin and tissue, said body having a side opening disposed somewhat rearwardly of said piercing extremity for defining a mixing and pickup area of predetermined length and width, said body having means at its rear portion for connection with a suction conduit to effect withdrawal of a mixture of emitted blood and a mixing and carrier liquid, controlled liquid supply means having a discharge disposed in said pickup area for causing mixture of supplied liquid with blood in said area, said instrument comprising part of a system which employs an electronic instrument for measuring electrical conductivity of the flowing mixture of blood and liquid withdrawn from said body, and wherein, as electrical sensors for said instrument, the tip portion of said body is constructed of an electrically conductive metal and the rear portion of said body is also constructed of an electrically conductive metal, and the interconnecting medial portion of said body is constructed of a substantially rigid material having substantially no electric conductive qualities, and electric conductors extending from said forward and rearward portions of said body to terminals of said instrument.
 6. A new method for automated determination of bleeding time and blood loss which consists in: forming a penetration in capillary tissue subepidermally with a cannula to form an incision in said tissue of predetermined length and width, said cannula being provided with a piercing tip and a side opening spaced therefrom, said side opening having longitudinal cutting edges and at least one shoulder defining the boundaries thereof, said cannula being inserted into said tissue in a direction substantially parallel to the skin with the side opening facing away from the skin so that the incision is formed along the bottom surface of the penetration, said cannula further providing a mixing and pickup space in said penetration directly above said incision formed by the boundaries of said side opening, supplying a predetermined small flow of a mixing and carrier liquid to said pickup space, withdrawing from said pickup space a mixture of emitted blood and said liquid, and by instrumentation responsive to the mixture flow determining the time bleeding takes place before clotting of said incision and also determining electrically the quantity of blood emitted during said test and the flow pattern.
 7. The combination of steps set forth in preceding claim 6 wherein said instrumentation includes in the withdrawn flow of emitted blood and carrier liquid, the passing therethrough of an electrical current with suitable sensors to determine change in the conductivity of the mixture during flow. 